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Hello all. I have a Craftsman model 917370561 lawn mower with a briggs stratton engine. It began misfiring, so I gave it a tune up (change oil, filter and spark plug). It continued misfiring and hard to turn on so I rebuilt the carb with the Briggs Stratton Carb rebuilt kit and also changed the primer bulb. It still misfiring and hard to turn on. I actually have to prime it 6-10 times for it to turn on and then misfires as it is on. If I turn it off and try to turn it right back up, i have to reprime which was not the case before. I then removed the filter housing and primed it and did not see any gas coming out from the tubing into the carb throttle body chamber. Actually sometimes it does come out and other times it does not. Any idea what might be causing this? Do I need a new carb or something else? Any info greatly appreciated. Thanks

The primer bulb is in the air filter housing, and sends a pulse of air into the carb where the base and carb meet. Sometimes you have to put a light coat of sealant on both sides of the gasket between the filter housing and carb to make it seal and prime like it should, but not too much or you will clog the passageway.

The misfiring, well, that is another thing. When you get it running, leave the air filter and cover off, then carefully partially block the air intake of the carb, and see if the engine runs any smoother. If so, then there is still a restriction in the carb.

Fish thanks for your info. I did just that once started, removed filter and housing and covered the intake as much as possible and it idled much better. So it appears problems with Carb. Might just buy a new carb as it will probably take much more time to figure out then the investment unless you have an idea what to look at? Thanks again

I would remove the carb and take it to a good repair shop to have it cleaned and rebuilt with a new float needle and seat.

hgiljr said:

Fish thanks for your info. I did just that once started, removed filter and housing and covered the intake as much as possible and it idled much better. So it appears problems with Carb. Might just buy a new carb as it will probably take much more time to figure out then the investment unless you have an idea what to look at? Thanks again

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I chased a similar problem like this on mine for months then I finally broke down, and bought a new carb it has been running perfect since then. Is it the plastic carb?

What all was in the rebuild kit? What about the bottom bowl nut? Did you change that out? If so, was it identical? If not, did you thoroughly clean it, all of it's little holes?

While the carb was apart, did you clean the holes up in the column where the bowl bolts on?

Clean the carb then use a overhaul rebuilt kit or buy a new carb.

Any chance the new spark plug has a crack in the ceramic portion of the plug? I have had this happen before.